New radiation-resistant circuits could aid work in damaged nuclear power plants

These two logic gates (XOR on the right, AND on the left) are made of microscopic mechanical parts and designed to resist ionizing radiation that fries conventional silicon electronics (Image: Massood Tabib-Azar/University of Utah)

High-radiation environments are a silicon microchip's worst nightmare and even state-of-the-art radiation-shielded circuits can fry after just a couple hours of exposure. Now engineers at the University of Utah have come up with a micro-electromechanical system that could be used to build robots and computers that are impervious to such conditions and may help us deal with high bursts of space radiation, damaged nuclear power plants or even the aftermath of a nuclear attack.

Electronic devices need a semiconductor channel to carry current. But when radiation strikes a microchip, it creates a second current that interferes with the normal state of affairs, making the original signal incomprehensible. We can use radiation-resistant materials (such as lead) to contain the problem, but this won't work for very long under the most extreme conditions - such as when we use remotely controlled robots to try and contain the consequences of a nuclear meltdown.

The micro-electromechanical systems (MEMS) developed at the University of Utah don't have this problem because they do away with semiconductor channels altogether. Instead, each device has two tungsten electrodes separated by a very narrow gap. When charged, the electrodes attract each other and touch, allowing the current to flow.

Silicon electronics are significantly faster, smaller and more reliable than your typical MEMS component, but the ones developed at the University of Utah have some interesting features that help fill what would otherwise be an insurmountable gap.

Each of the MEMS devices acts as a logic gate, reducing the number of components needed by a factor of 10 while increasing speed and reliability. Also, the very narrow gaps between the bridges in the logic gates means the devices require a voltage of 1.5V, or only a tenth of what is normally needed in a device of this type. Moreover, each logic gate measures about 25-by-25 microns and is only a half-micron thick.

Shown here are three kinds of micro-electro-mechanical systems (MEMS) circuits built from microscopic mechanical devices, known as “logic gates,” designed to resist ionizing radiation. The circuits are a 2-bit multiplexer (left), a 1-bit full adder (center) and a 2-bit full adder (right) (Image: Massood Tabib-Azar/University of Utah)

To put their component to the ultimate test, the researchers dropped a circuit they produced using their technology into a nuclear reactor. After long periods of exposure, it was still working seamlessly and with no degradation.

The research will be published later this month on the journal Sensors and Actuators. Given sufficient funding, the researchers say the next stage would be to build a simple computer using their design.